1. Field of the Invention
The present invention relates to a wireless communication system, and more particularly, to a method of paging in a wireless communication system.
2. Discussion of the Related Art
First of all, an idle mode of a mobile station and a paging group will be described.
A broadband wireless access system supports an idle mode to minimize power consumption of a mobile station. The idle mode means that a mobile station can receive downlink (DL) broadcast traffic even though it is not subscribed to a specific base station when moving at a wireless link environment where multiple base stations are provided.
The mobile station does not need to perform a handoff procedure during an idle mode when moving between base stations included in a paging zone. In this case, the mobile station is not required to transmit uplink information for the handoff procedure, whereby power consumption can be reduced.
The paging zone means a zone covered by a paging group that includes a plurality of base stations, and paging means a function for identifying location (for example, any base station or any exchange station) of a mobile station when a call signal is generated. At this time, a paging group represents a logical group. The paging group is intended to provide a downlink with a neighboring zone that can be paged, if there is any traffic decided to target the mobile station.
The paging group can include one or more base stations. Also, one base station can be included in one or more paging groups. The paging group is defined by a management system. The paging group can use a paging group-action backbone network message. Also, a paging controller can manage a list of mobile stations, which are in an idle mode, by using a paging announcement message which is one of backbone network messages, and can manage initial paging of all base stations that belong to a paging group.
If the mobile station asks the base station to switch it to the idle mode, the base station can switch the mobile station to the idle mode by forwarding its paging group ID to the mobile station.
Next, a paging procedure according to the related art will be described.
If a call or packet of the mobile station is transmitted to the paging controller while the mobile station is being in the idle mode, the paging controller transmits a paging message to all base stations within the paging group, and the base stations within the paging group, which have received the paging message, broadcasts a paging advertisement message to mobile stations managed by them. The mobile station determines whether to shift to a normal mode or remain in the idle mode by receiving the paging advertisement message, which is transmitted from the base station, for an available interval. Namely, if the paging controller pages the mobile station, the mobile station enters the normal mode and performs communication with the base station.
However, a problem occurs in that the mobile station should receive the paging message per paging offset even in the case that there is no paging message transmitted to the mobile station. This could lead to power consumption.